1. Field of the Invention
The invention relates to plastic metal working and more particularly to devices for corrugating a sheet material with forming staggered cut corrugations.
The proposed invention may be used in devices for corrugating a sheet material with forming staggered cut corrugations, from materials having a different thickness, hardness, chemical composition and degree of surface roughness, and utilized as heat exchange inserts in heat exchange apparatus having wide applications.
2. Description of the Prior Art
Known in the prior art is a device for corrugating sheet material, comprising two interacting shafts made up of a plurality of cutting and forming plates provided with cutting edges arranged on involute teeth, the teeth of the adjacent plates of each shaft being offset through half a tooth pitch. The toothed shafts of such a device combine a sheet material feed mechanism with punches which corrugate the material and form staggered cut corrugations. The apex angle of a corrugation made by this device cannot be less than 100.degree.. This makes such heat exchange inserts less compact as the pitch of the corrugation is more than 1.5 times greater than its height. Besides, in the process of cutting the sheet material burrs appear on the edges of cuts and grow in size as the operating time of the device increases. The value of an incomplete cutting of the sheet material at a joint of cuts is substantial. The quality of the corrugated heat exchange inserts with cut corrugations made by this device is rather low which limits its use in heat exchange apparatus.
Also known in the prior art is a device for corrugating a sheet material with forming staggered cut corrugations, comprising a mechanism for feeding sheet material to two punches installed for reciprocating motion on both sides of the material in the plane perpendicular to the plane of the material and associated with a mechanism for reciprocating the punches over the surface of the material in the plane perpendicular to the direction of its feeding. The punches are made in the form of combs provided with forming and cutting edges. The teeth of one punch are arranged opposite the tooth spaces of the other punch.
The profile of each tooth of the punches in cross-section is made in the form of an isosceles triangle having a rounded-off apex.
The sheet material is corrugated and staggered cut corrugations are formed in the following way.
The teeth of one punch force the sheet material by their rounded-off apexes into the tooth spaces of the other punch. At the same time the cutting edges of the rounded-off apex incise the sheet material. The final cutting is accomplished by the cutting edges of side surfaces and the final forming of a corrugation profile is effected by the side surfaces and the rounded-off apex of the punches.
The angle of cutting made by the side forming surfaces of the punches must not be less than 30.degree. which is necessary to ensure the process of cutting the sheet material. As a result, the minimum pitch of a corrugation obtained by such a method of manufacture is restricted by the height of the corrugation and cannot be less than three quarters of the corrugation height. Such corrugated heat exchange inserts are less compact which limits their use in heat exchange apparatus.
Besides, due to a wearing effect of the sheet material on the cutting edges of punches, the latter get blunted with time. Burrs on the edges of cuts in the sheet material grow in size. The value of an incomplete cutting of the sheet material at a joint of cuts increases. As a result, the thermohydraulic effectiveness and quality of the corrugated heat exchange inserts made by this device get substantially declined in the process of the device operation and a frequent replacement of the punches is required.